P38 cam sensor

hi all - I've done a quick search and can't find anything, so thought I'd post a new thread

My wife has an early ('95) P38 4.0 base. It has a misfire when stone cold - clears within a mile and is fine after that. Its a bit sluggish as well. My local landie specialist (Mercia 4x4 in Cannock, Staffs) has hooked up the diagnostic and its showing as the cam sensor. I guess if the sensor is failing (or failed), then a retarded ignition will cause poor starting and lack of urge on acceleration, so it all sounds about right

What doesn't sound right is the price - £190

The car has already swallowed a good few quid (engine three years ago, aircon compressor two years ago, full autobox rebuild this year), so I was half expecting a stiff bill, but c'mon - almost two hundred notes for a sensor?

So - two questions.....

1) Does anyone know of a cheaper source of cam sensors?
2) Can someone give me an approximate value (or range of values) for the car (once fixed, of course) - 1995 P38 4.0 base, cloth, climate, 152k, FSH (main dealer and specialist), new engine @ 110k, new gearbox a couple of months ago, 18" Hurricanes, with decent Pirellis, everything works, its mostly straight, apart from a cracked rear bumper, where wifey argued with a telegraph pole (result was a score draw, one cracked bumper, one cracked telegraph pole )

if the value is as low as I fear its going to be, I'll get wifey the Mini she wants, and start using the rangie for what it was designed for, without fear of getting a shouting at when I scratch it. I live 2 miles from Cannock Chase in Staffs, so plenty of half-decent offroading to be had (albeit at a cost)

Thanks in advance

NigelO said:

My wife has an early ('95) P38 4.0 base. It has a misfire when stone cold - clears within a mile and is fine after that. Its a bit sluggish as well. My local landie specialist (Mercia 4x4 in Cannock, Staffs) has hooked up the diagnostic and its showing as the cam sensor. I guess if the sensor is failing (or failed), then a retarded ignition will cause poor starting and lack of urge on acceleration, so it all sounds about right

Click to expand...

A failed cam sensor won't do anything to ignition timing. The cam rotates at half engine speed and the sensor is used to identify which of the two revs in the two-rev-four-stroke cycle the engine is on, i.e. at TDC-Cyl1 it shows whether cylinder 1 is at the top of the compression stroke or the exhaust stroke.

Ignition will either be by distributer or by double ended coils running wasted spark where each cylinder fires once/rev so cam sensor is irrelevant for that.

The cam sensor is only used by the fuelling for timing the start of the injection pulse (or more crucially the end!) when running SEquential Fuel Injection (SEFI).

Not too sure that it would cause a misfire tho' except maybe on sharp transients (stepping in hard on the throttle), it could maybe mess up the emissions a bit but misfiring seems an unlikely end result.


I personally wouldn't expect to pay much more than £50 for a cam sensor .....